Bafang BBS02 500w 36v shutoff issue

[bobbacon]

Hi. I've got a problem and I thought I'd fish for help here, maybe someone else have had the same problem. The system shuts down randomly, and at first I thought it was poor connectors, but I replaced them and it keeps occurring. I recently had the battery BMS replaced by an e-bike shop, and when I got the battery back, the bike wouldn't start, and after fiddling with the connectors it turned on, so I thought I'd solved the problem. After that it happened when going over rough terrain, so I figured vibration was the issue, but then it started happening when climbing on brand new asphalt. It's very inconsistent. Today I went full blast up really steep hill with heavy groceries in my backpack to see if it had something to do with the BMS not being able to handle the amps, but it was fine the whole way up, and that hill really makes this thing work. I thought of overheating, but that's not the issue, it sometimes happens right away when I take the bike out, when motor is cool. When it happens, I have to disconnect the battery for a few seconds, then it starts up again. I've opened the unit up and checked the wires from the controller to the motor, and everything was fine.
My gut feeling tells me there's something wrong with the battery, so I wanted to ask around before I contact the shop.
Appreciate any ideas,

Simon

 

[amberwolf]

If it's "random" then it's a connection problem, almost certainly.

But it doesn't have to be at the connectors, it could be a broken wire inside the insulation anywhere along the wire length.

Could also be a bad crimp or solder at a contact in a connector, or a connector pin that is pushed back out of the connector when plugged in but looks normal when pulled out.

 

[bobbacon]

If it's "random" then it's a connection problem, almost certainly.

But it doesn't have to be at the connectors, it could be a broken wire inside the insulation anywhere along the wire length.

Could also be a bad crimp or solder at a contact in a connector, or a connector pin that is pushed back out of the connector when plugged in but looks normal when pulled out.

Hi, thanks for replying. The issue has gone from usable bike to unusable. Yesterday it started shutting down as soon as the motor needed to work. If I lift the back wheel and go full throttle it's fine, but a minor climb or basically just going on the flat results in shutdown, with the exception of lowest gear (34T + 44T Chain ring, 20" wheels) on the flat. Last few weeks I was able to climb the ultra steep sometimes without issues, so I'm a bit puzzled. I just took the motor apart again to recheck all the connectors and such, all looks fine. Can't find any broken wires or broken insulation... More ideas?

 

[amberwolf]

You could have multiple problems, rather than just one, and all could be intermittent, making it harder to find.

Did you check all the wires, contacts, plugs, etc., everywhere on the entire bike? Including inside the controller, if necessary. If so, I'd recheck the battery connections (inside it if necessary).

Or it could be a cell that's drained down too far, so that any load on it is enough to trigger BMS shutdown for cell LVC. You'd need to measure each cell voltage with and without a load to test for that. There's a lot of battery troubleshooting threads that describe this method and the results you should see, but you'd have to poke around the forum (mostly in battery section) for them. Might be something in the ES wiki but not sure.

 

[bobbacon]

You could have multiple problems, rather than just one, and all could be intermittent, making it harder to find.

Did you check all the wires, contacts, plugs, etc., everywhere on the entire bike? Including inside the controller, if necessary. If so, I'd recheck the battery connections (inside it if necessary).

Or it could be a cell that's drained down too far, so that any load on it is enough to trigger BMS shutdown for cell LVC. You'd need to measure each cell voltage with and without a load to test for that. There's a lot of battery troubleshooting threads that describe this method and the results you should see, but you'd have to poke around the forum (mostly in battery section) for them. Might be something in the ES wiki but not sure.

Thanks. I did check the controller for a second time. When battery went to repair the cells were fine, but I'll check them again and the connections inside too. As I said it started after the BMS was changed and of course the bike shop didn't run it on a bike long enough for it to show. Hopefully I'll find something.. Ah, of course, there's a LVC both in the BMS and the controller, so it could be either one...Cheers

 

[bobbacon]

Hi again. I've found the solution. I had completely forgot to reset the BMS. I unplugged it for a half hour and reconnected, and now it works fine. I realized that I had changed my charging to only 90%(on recommendation from EM3ev.com, to prolong battery life) and the BMS hadn't balanced the cells, or at least that's what I imagine. They said the cells only needed to be balanced every month or so. Maybe it doesn't work on my BMS very well. Hopefully it will run from now on, and I'll have to charge it to 100% every time I suppose. Thanks for the help!

Simon